Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 5 2 2009 10.5194/cpd-5-1163-2009 http://www.clim-past-discuss.net/5/1163/2009/ http://www.clim-past-discuss.net/5/1163/2009/cpd-5-1163-2009.html http://www.clim-past-discuss.net/5/1163/2009/cpd-5-1163-2009.pdf 1163 1185 2009-03-31 Investigating the impact of Lake Agassiz drainage routes on the 8.2 ka cold event with climate modeling Y.-X. Li li@tulane.edu H. Renssen A. P. Wiersma T. E. Törnqvist Department of Earth and Environmental Sciences, Tulane University, New Orleans, Louisiana 70118-5698, USA Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, The Netherlands Deltares, Subsurface and Groundwater Systems, Utrecht, The Netherlands The 8.2 ka event is the most prominent abrupt climate change in the Holocene and is widely believed to result from catastrophic drainage of proglacial lakes Agassiz and Ojibway (LAO) that routed through the Hudson Bay and the Labrador Sea into the North Atlantic Ocean, and perturbed Atlantic meridional overturning circulation (MOC). One key assumption of this triggering mechanism is that the LAO freshwater drainage was spread over the Labrador Sea. Recent data, however, show no evidence of lowered δ¹⁸O values from the open Labrador Sea around 8.2 ka. Instead, negative δ¹⁸O anomalies are found close to the east coast of North America, extending as far south as Cape Hatteras, North Carolina, suggesting that the freshwater drainage was probably confined to a long stretch of continental shelf before fully mixing with North Atlantic Ocean water. Here we conduct a sensitivity study that examines the effects of this southerly drainage route on the 8.2 ka event with the ECBilt-CLIO-VECODE model. Hosing experiments of four different routing scenarios, where freshwater was introduced to the Labrador Sea in the northerly route (R1) and to three different locations (Grand Banks – R2, George Bank – R3, and Cape Hatteras – R4) on the southerly route, were performed with 0.45 m sea-level equivalent (SLE), 0.90 m SLE, and 1.35 m SLE of freshwater introduced over 5 years to investigate the routing effects on model responses. 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